1. Field of the Invention
This invention pertains to modular chemical distribution substrate block designs used in the semiconductor industry and, more particularly, to the mechanical features of the substrates and their modular components, their accessibility from top surfaces for assembly and disassembly, and the specific mechanical dimension requirements of such substrate block design.
2. Description of Related Art
In the semiconductor industry and well as in other industries, modular gas substrates are used for directing and controlling the flow of gas reactants and other chemicals (i.e. liquids). Through the use of truly modular substrates and components, not only can worn components be more easily replaced but also the design of the gas delivery system can be changed. For example, in chemical etch processes, there are demanding requirements for quickly changing out gas lines periodically due to corrosion of the lines, and/or to partially or completely reconfigure the etch system during maintenance. FIG. 1A shows a prior art system for an etch process tool used in the semiconductor fabrication industry. Conventional methodology for providing such gas paths uses stainless steel conduit or tubing 11 (typically 1/4" O.D., 3/8" O.D., or 1/2" O.D.), which is welded between each gas controlling component 13. Such conventional technology has the disadvantages of taking too much time to change-out or repair components 13 and being costly to reconfigure the conduit (tubing) path 11. Therefore, truly modular blocks for use in these applications are desired and needed.
Although for years Asian and United States suppliers of such modular chemical delivery substrates have used a variety of methods for bolting or otherwise fastening together modular substrate blocks, no previous approach to date has addressed the need for entirely top accessible components for particular applications. For example, FIG. 1B is a diagram of a prior art modular substrate design whereby the individual blocks 14 are fastened together with horizontal, full length bolts 12, 30 throughout an entire assembly 15 of blocks 14. Although this prior art system can be assembled rather quickly (typically only two 2-inch bolts per axial connection), problems with this design raise several safety, disassembly and repair concerns.
One such problem with the prior art system in FIG. 1B is the amount of deflection of the long bolts 12 when subjected to the torque required to provide appropriate sealing integrity between the substrate sealing joints 17. Effectively, the basic deflection force of a bolt 12 can be calculated with the following formula: DEFLECTION=PL/AE, wherein P is the amount of force load upon an axial connection of any adjoining blocks 14 in series (the deflection potential), L is the length of the bolt 12, A is the cross-sectional area of the bolt 12, and E is the modulus of elasticity of the bolt 12 based on its material composition. If it is assumed that all equipment suppliers of such modular substrate technology use 300 series or better materials for the fastener components, then E is a constant for any length bolt 12. Likewise, in these types of modular gas system designs, typically the designer is mechanically constrained to using fastener diameters of 1/4" (6.35 mm) or smaller, and thus A can be considered relatively constant. In summary, if A and E are constant, then as the designer increases the length of the bolt 12 L, there will be a corresponding linear increase in the deflection force of the bolt 12 which is conveyed to the fastened substrate joints. If the deflection force is high enough, it may cause a potential seal integrity loss at the axial (joint-to-joint) connections 17. Another concern with the extended length fastener design shown in FIG. 1B is the fact that if a user were to require removal of any one substrate block 14 in the long fastener assembly 15, the entire assembly 15 and respective sealing joints 17 would be exposed to atmosphere. This problem presents a potential safety and contamination issue with corrosive and toxic chemical delivery applications.
FIG. 1C is a drawing of another prior art modular substrate design whereby the individual blocks 14 are fastened together via localized bolting of each substrate-to-substrate or axial joint connection 16, and the entire assembly is connected te mounting brackets 26. This, design dramatically reduces or eliminates the concern for deflection potential by localizing fastener sealing strength, integrity, and length. Use of such a localized fastener design also reduces the number of sealing joints 10 exposed to atmosphere for any given substrate block 14 within the assembly. However, the localized fastener substrate joining design shown in FIG. 1C also has a limitation regarding disassembly. Referring now to FIG. 1D, which depicts a top view of the substrate design shown in FIG. 1C, if the user were to place multiple substrate assemblies side-by-side (typically on 1.6" (40.64 mm) to 2" (50.8 mm) spacing), many of the axial fasteners 18 as shown in FIG. 1D cannot be accessed because the fastener locations lie under the top accessible surface of the blocks 14. Clearly, a method of assembling the substrate blocks which overcomes the disadvantages of the prior art is needed.